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At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Summary of NASA storm hazards lightning research, 1980-1985

Lightning swept-flash attachment patterns and the associated flight conditions were recorded from 1980-1985 during 1378 thunderstorm penetrations and 690 direct strikes with a NASA F-106B research airplane. The individual lightning attachment spots, along with crew comments and onboard photographic data have been used to identify lightning swept-flash attachment patterns and the orientations of the lightning channels with respect to the airplane. The altitudes, ambient temperatures, and the relative turbulence and precipitation levels at which the strikes occurred also are summarized and discussed, with an emphasis on the differences between high and low altitude strikes.

Fisher, B. D.↗
NASA NTRS1986

F-106 data summary and model results relative to threat criteria and protection design analysis

The NASA F-106 has acquired considerable data on the rates-of-change of EM parameters on the aircraft surface during 690 direct lightning strikes while penetrating thunderstorms at altitudes from 15,000 to 40,000 feet. The data are presently being used in updating previous lightning criteria and standards. The new lightning standards will, therefore, be the first which reflect actual aircraft responses measured at flight altitudes.

Pitts, F. L.↗
NASA NTRS1986

Precipitation estimation using passive microwave radiometry at 92 and 183 GHz - Aircraft results

The applications of satellite and aircraft sensors to precipitation estimation are discussed. The advanced microwave moisture sensor and imagery and the PPI photographs and digital radar data are described. The aircraft microwave sensor and radar imagery representing the relationships between patterns and gradients of brightness temperature, T(B), and echo intensities for three cases (evolution of an oceanic squall line, convection over land, and intense thunderstorms over land) are examined and compared. The observed T(B)s are also compared with the theoretical calculations of Wu and Weinman (1984) and Szejwach et al. (1986). The observations of convective precipitation from an aircraft microwave radiometer operating at 92 and 183 GHz reveal that the areas of T(B) much colder than atmospheric temperature are positively correlated with regions of higher radar reflectivity, and the patterns and gradients of T(B) are similar in appearance to the radar echoes.

Hakkarinen, Ida M.↗
NASA NTRS1986

Satellite contributions to convective scale weather analysis and forecasting

Severe weather phenomena which are amenable to remote sensing by satellite instruments and having resolution fine enough to discern mesoscale features are described. GOES satellites acquire imagery with 1 km resolution in the visible band and 8 km at IR wavelengths. Animation of the images allows tracking the evolution and motions of clouds, which are the prime indicators of convective activity. Sample satellite imagery of sea, lake and river breezes which reveal differential heating processes, the effect of early morning cloud cover, thunderstorm outflow processes, and mesoscale convective systems are provided. Techniques for analyzing the satellite data to predict the onset of severe weather are discussed.

Purdom, James F. W.↗
NASA NTRS1987

Turbulence structure in microburst phenomena

The efect on turbulence of a variable mean wind along the flight path of an aircraft is modeled and analyzed. It is found that the effect of a variable head or tail wind alters the magnitude of the length-scale of sensed microburst turbulence, rendering turbulence more random than usually encountered in the upper atmosphere. This, coupled with accompanying aerodynamic lift loss experienced during the headwind-to-tailwind swing, is what collectively creates the hazardous environment for a microburst-encountering aircraft attempting to land during a thunderstorm.

Trevino, George↗
NASA NTRS1987

Severe storm identification with satellite microwave radiometry - An initial investigation with Nimbus-7 SMMR data

The use of satellite passive microwave observations for the detection of severe thunderstorms is investigated. Nimbus 7 SMMR data obtained from 1979 to 1980 over the U.S. east of 105 deg W are analyzed. The relative temperature brightnesses of the severe storms are examined; it is observed that temperature brightness decreases as the storm severity increases. The temperature brightness data were transformed into a quantitative measure of storm detection ability using the critical success index of Donaldson et al. (1975). Critical success indices of 0.32, 0.48, and 0.38 were obtained for the low-brightness-temperature thresholding of severe versus nonsevere storms during 1979, 1980, and 1979 and 1980 combined, respectively. The data reveal that the geostationary passive microwave imaging capability at 37 GHz is applicable to the detection and monitoring of severe convective storms.

Howland, Michael R.↗
NASA NTRS1987

The microbursts of 22 June 1982 in JAWS

The development of several large thunderstorms that occurred on June 22, 1982 within the Joint Airport Weather Studies (JAWS) network near Denver, Colorado is examined together with that of six microbursts and one microburst line produced by the storms. From the analysis of single and multiple Doppler radar and surface network data, it is concluded that the microbursts on June 22 were predominantly driven by microphysical and related thermodynamic effects due to precipitation loading and water-phase change; dynamic effects did not appear to be of primary importance. Surface network observations permitted identification of some of the microbursts, but early detection was not possible.

Hjelmfelt, M. R.↗
NASA NTRS1986

Cloud-to-ground lightning activity in mesoscale convective complexes

An analysis of the evolution of cloud-to-ground lightning discharges attending convective storms in mesoscale convective systems was conducted in the framework of the mesoscale convective complexes (MCCs) life cycle. The lightning discharge data were acquired by a commercially available lightning detection and location system. Peak rates averaged 42/min for the MCCs analyzed; these rates are comparable to the highest observed rates within other mesoscale storm systems and are greater than 20 times the rates previously observed in isolated thunderstorms. Lightning damage occurs with half of the MCCs and is most frequent between the development and the mature phases of the MCC life cycle. The most active period is also characterized by the greatest average number of discrete strokes and largest fraction of multiple-stroke discharges. The total cloud-to-ground lightning activity and maximum flashing rate do not appear to be directly related to either the size of the cloud shield or total duration of the MCC.

Goodman, S. J.↗
NASA NTRS1987

Short-term forecasting of lightning based on the surface wind field at Kennedy Space Center

Cloud-to-ground lightning is related in time and space to surface convergence for 244 days during the summer over a 790 sqkm network. The method uses surface convergence, particularly the average over the area, to identify the potential for new, local thunderstorm growth, and can be used to specify the likely time and location of lightning during the life cycle of the convection. A threshold of 0.0000075/sec change in divergence is used to define a convergence event, and a separation of 30 min between flashes defines a lightning event. Time intervals are found to be on the order of 1 hr from beginning convergence to first flash, and (CH110) 2 hr from beginning convergence to the end of lightning. Major differences between the convergence-lightning relationships based on low-level mean onshore and offshore flow are noted.

Watson, Andrew I.↗
NASA NTRS1986

Convective scale interaction: Arc cloud lines and the development and evolution of deep convection

Information is used from satellite data and research aircraft data to provide new insights concerning the mesoscale development and evolution of deep convection in an atmosphere typified by weak synoptic-scale forcing. The importance of convective scale interaction in the development and evolution of deep convection is examined. This interaction is shown to manifest itself as the merger and intersection of thunderstorm outflow boundaries (arc cloud lines) with other convective lines, areas or boundaries. Using geostationary satellite visible and infrared data convective scale interaction is shown to be responsible for over 85 percent of the intense convection over the southeast U.S. by late afternoon, and a majority of that area's afternoon rainfall. The aircraft observations provided valuable information concerning critically important regions of the arc cloud line: (1) the cool outflow region, (2) the density surge line interface region; and (3) the sub-cloud region above the surge line. The observations when analyzed with rapid scan satellite data, helped in defining the arc cloud line's life cycle as 3 evolving stages.

Purdom, James Francis Whitehurst↗
NASA NTRS1988

Atmospheric Science and Remote Sensing Laboratory

During the contract year, scientific research on lightning and lightning hazards was carried out for the Atmospheric Electricity Group in the MSFC Remote Sensing Branch (ED43). These tasks included research on modeling the interaction of lightning optical pulses and cloud particles, estimating lightning hazard threats to the STS system, a small field project to determine the charge structure of winter and stratiform thunderstorms, and analysis of optical pulse data. These activities were performed in conjunction with the ED43 mission to develop a lightning mapper to be placed on one of the GOES-next operational satellites.

Mach, Douglas↗
NASA NTRS1988

Loran-C monitor correlation over a 92-mile baseline in Ohio

Two Loran C monitors, at Galion and Athens, Ohio, were operated over a one-year period, measuring chain 9960 Time Delay (TD) and Signal to Noise Ratio (SNR). Analysis of data concentrated on correlation of short term TD variations during the winter months of 1985 to 86, over the 92 nm baseline. Excellent correlation was found, with slight additional improvement possible if local temperature is also included in the analysis. Although SNR and TD effects were suspected during the presence of thunderstorms near the monitors, the scope of the study did not permit storm by storm analysis. A computer tape data base of all measurements was produced, with measurements at both sites included. Data recording and analysis concentrated on the fall and winter months of September 1985 to February 1986.

Lilley, Robert W.↗
NASA NTRS1988

General-aviation's view of progress in the aviation weather system

For all its activity statistics, general-aviation is the most vulnerable to hazardous weather. Of concern to the general aviation industry are: (1) the slow pace of getting units of the Automated Weather Observation System (AWOS) to the field; (2) the efforts of the National Weather Service to withdraw from both the observation and dissemination roles of the aviation weather system; (3) the need for more observation points to improve the accuracy of terminal and area forecasts; (4) the need for improvements in all area forecasts, terminal forecasts, and winds aloft forecasts; (5) slow progress in cockpit weather displays; (6) the erosion of transcribed weather broadcasts (TWEB) and other deficiencies in weather information dissemination; (7) the need to push to make the Direct User Access Terminal (DUAT) a reality; and (7) the need to improve severe weather (thunderstorm) warning systems.

Lundgren, Douglas J.↗
NASA NTRS1985

The 1983 direct strike lightning data, part 1

Data waveforms are presented which were obtained during the 1983 direct strike lightning tests utilizing the NASA F106-B aircraft specially instrumented for lightning electromagnetic measurements. The aircraft was operated in the vicinity of the NASA Langley Research Center, Hampton, Virginia, in a thunderstorm environment to elicit strikes. Electromagnetic field data and conduction currents on the aircraft were recorded for attached lightning. Part 1 contains 435 pages of lightning strike data in chart form.

Thomas, Mitchel E.↗
NASA NTRS1985

The 1983 direct strike lightning data, part 2

Data waveforms are presented which were obtained during the 1983 direct strike lightning tests utilizing the NASA F106-B aircraft specially instrumented for lightning electromagnetic measurements. The aircraft was operated in the vicinity of the NASA Langley Research Center, Hampton, Virginia, in a thunderstorm environment to elicit strikes. Electromagnetic field data and conduction currents on the aircraft were recorded for attached lightning. Part 2 contains 443 pages of lightning strike data in chart form.

Thomas, Mitchel E.↗
NASA NTRS1985

The 1983 direct strike lightning data, part 3

Data waveforms are presented which were obtained during the 1983 direct strike lightning tests utilizing the NASA F106-B aircraft specially instrumented for lightning electromagnetic measurements. The aircraft was operated in the vicinity of the NASA Langley Research Center, Hampton, Virginia, in a thunderstorm environment to elicit strikes. Electromagnetic field data and conduction currents on the aircraft were recorded for attached lightning. Part 3 contains 446 pages of charts depicting additional lightning strike data.

Thomas, Mitchel E.↗
NASA NTRS1987

Space Transportation System Meteorological Expert

The STS Meteorological Expert (STSMET) is a long-term project to acquire general Shuttle operational weather forecasting expertise specific to the launch locale, to apply it to Shuttle operational weather forecasting tasks at the Cape Canaveral Forecast Facility, and ultimately to provide an on-line real-time operational aid to the duty forecasters in performing their tasks. Particular attention is given to the development of an approach called scenario-based reasoning, with specific application to summer thunderstorms; this type of reasoning can also be applied to frontal weather phenomena, visibility including fog, and wind shear.

Beller, Arthur E.↗
NASA NTRS1987

Airborne Doppler lidar observations of convective phenomena in Oklahoma

On 30 June 1981, the wind fields around a variety of convective clouds, ranging from large thunderstorm complexes to isolated cumulus congestus, were observed in Oklahoma using an airborne Doppler lidar operated by NASA. By steering the pulsed infrared laser beam alternately along differing horizontal directions, a network of independent radial velocity measurements is obtained, which permits high-resolution synthesis of the full horizontal wind vector field in a swath adjacent to the aircraft flight track. The bright reflections of the laser signal by cloud surfaces permit direct identification of the locus of cloud edges, information which is prerequisite to detailed study of the relationships between the winds inside and outside clouds. The horizontal wind fields derived from the lidar data reveal waves and vortices along the gust front of a storm which eventually produced a gust-front tornado, and cloud-scale convergence patterns around an isolated cumulus congestus. Despite the presence of some questionable data associated with undersampling and delayed recording of certain aircraft motion parameters, most of the lidar results appear consistent with cloud photographs made during the experiment, with surface meteorological data, with aircraft flight-level wind data, and with previous observational and theoretical work.

Mccaul, Eugene W., Jr.↗